JPS58159992A - Method and device for manufacturing space grating of reactor through pulse laser welding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for manufacturing nuclear reactor structural elements such as spacer grids by laser laser welding, and more generally to small thin It concerns the application of such a method to the manufacture of devices for inserting parts.

To prevent swaying of the fuel rods P in a nuclear reactor, spaced or mixed grids are often placed along the assembly. These lattices intersect in pairs and the tips Pt-
It consists of a system of thin plates that define a fixed number of racks to hold. Cooling fluid is circulated between these plates and the ronds and can be provided in a grid with fine mixing fins. The plane forms an angle with the plane of the lamina to deflect the liquid flow and homogenize the cooling liquid. mixed road
.

The children are generally very small (about several tens of minutes thick)
+, on the other hand, the size is about 10 to 20 pieces).

Currently, mixed grids are usually made from Inconel, an alloy that is easy to assemble by soldering or hard soldering, but this metal has good properties in the first circuit, producing long-life activation products such as Conomult 60. It has the disadvantage of being a neutral absorbent. For this reason, interest has turned to other alloys, particularly zirconium alloys such as Zircaloy 4. Although the latter have good resistance to corrosion by water, they are more difficult to weld than Inconel, and for that reason they have hitherto not been used for this purpose.

First, Zircaloy is difficult to solder and this method is not straightforward. Moreover, because the grid is small, there are positioning problems when using a torch and there is a risk of severe heating of the metal which can cause deformation and oxidation of the plate.

The present invention aims to eliminate these disadvantages by means of a welding method for grids, in particular zirconium alloy grids, which can eliminate all risks of deformation and oxidation.

According to the main feature of this method, the grid consists of laminae that intersect with each other and thus defines a certain number of crosses.

The parts are then placed in a tight enclosure under controlled air and the cross sections are secured to laser-produced weld spots at each of their ends.

At present, laser welding is a particularly well-applied method for welding zirconium alloy grids.

Preference is given to the use of pulsed lasers, which can reduce the risk of heating and consequent deformation of the part.

According to another feature of the method of the invention, a laser beam radiation source is used which is located outside an enclosure, the enclosure being provided with at least one wall that is transparent to the wavelength of the laser beam used. The cage and its head are positioned so that the beam passes perpendicularly through the wall.

In many cases, the ends of the plates are attached to the belt or belt plate KW.

If greater mechanical strength is required for the manufactured element or grid, the cross sections are welded at least on the intersection points of the plates.

In this case, the welding is done differently. That is, weldments are made at two opposite dihedral corners of each cross section, and only at these two corners, the weldment arrangement is continuously along one plate, with two weldments on the - plane, There are then two welds on the other O side, which are carried out to the edges of the plate.

Particularly and preferably, when the plates intersect at right angles, the laser beam can be positioned Z in the plane subtending each two planes so that the intersection line of the plates forms an angle of approximately 45'.

According to another feature of the method according to the invention, a rigid frame of light alloy is placed around the outer retaining belt before the cross section ttm determination and/or before welding along the intersection points of the plates.

The plate is secured to the belt plate by welding two tenons provided at each end of the plate to two mortises provided in the belt plate. Welding is performed by laser means in spots and overlaps to obtain a continuous weld line.

According to a different aspect of this method, mirrors can be used to deflect and split the V-zer beam, which can perform several welds at the same time. and<
K can be formed simultaneously at two opposite dihedral angles of one cross section.

The invention also relates to a device for carrying out this method.

According to the main features of this device, it consists of: namely, a pulsed frame 4-radiation source, a controlled air-containing shell having at least one wall transparent to the wavelength of the beam used and a frame for holding or securing the grid during the welding operation; A tight enclosure in which the grid to be welded is placed.

According to a first aspect, the device includes means by which the frame can be replaced within the enclosure if the cross section is welded along the intersection of the plates. If welding is only carried out at the ends of the cross section, the device moves the enclosure and the frame at the same time. +5. ,l-11,,#i,L
, 1ilika. □Eoi 7. ; Sometimes some melt! ! Mirrors can be used to deflect and split the V-ser beam to accomplish this.

Finally, the invention also relates to a zirconium alloy mixed lattice obtained by the method of the invention. This allows the welding line to obtain a grid without any traces of contamination or oxidation.

FIG. 1 shows that the grid 1 consists of a group of plates, such as 2 and 4, which intersect each other at right angles and define a certain number of cross sections 6. FIG. Four plates such as 2 and 4 such as 4 are shown and these form two plates parallel to each other and perpendicular to the other groups of plates.

Although the number of plates shown in the figure has been reduced for clarity, in reality there are many more such plates. Thus, for the purpose of the test, a
The method of the invention was used to produce a Zircaloy grid 4 with two groups of 16 plates forming 2.5 x 12.5 - racks or cells.

Each cell receives a fuel rod, such as the rod Pc shown schematically by the blend line in FIG. The rod C is maintained by the forces exerted by four members provided in each rack (arrow 3 symbolizes the action of these members). Rotsu Pc is generally cut into the plate 2 and 4 in the form of an elastic sheet.

Naturally, slots such as 10 and 14 are provided along the plates 2 and 4, respectively, and fit together to form the cross section 6. If the grid is placed under controlled air in a tight enclosure (311 not shown), the first plant of the method according to the invention will be applied to the welding points at each end 7 of the cross s6 Consisting of fixing the cross s6, the laser beam, symbolized by the arrow down 1, is positioned along the intersection line of the plates 2 and 4.

The second factory has belts on all four sides of plates 2 and 4
or by fixing it to the belt plate 9. For this purpose, two tenons 8 are provided at the end of each plate 4,
These are introduced into the two holes 12 in the plate 9. Naturally the plate 9 has groups of two mortises 12 of the same number if there are plates like 4 in the grid. Hazo 8 #1
Welding to the borehole 12 is done by laser means by spot and over-q-lap to obtain a continuous weld.

The final step consists of fixing the 9ft belt plates together to produce an external protection belt for the grid. The plate 9 is again produced with a weld bead 13 by spot and overlap laser using a laser to obtain a continuous weld.
The ends are then assembled together.

The laser beam is placed outside the enclosure to minimize the volume of this enclosure.

Optionally and more easily, the steps of the method according to the invention can be reversed and the fixing of the cross section can be carried out after welding plates 2 and 4 to the belt plates and after welding the belt plates together. .

This leads to lattices with sufficient mechanical properties for use as spacing lattices in nuclear reactants. However, if increased strength is sought, it is advantageous to make a cross weld along the intersection of the plates, such that the weld is made over the entire length of the intersection or over a portion of it. be able to. In this case, the welding of each cross section 6 is carried out only in two opposite dihedral corners and from the four corners defined by the intersection of plates 2 and 4 only in these two corners.

Furthermore, weldments can be obtained in other ways. That is, along each plate 2 or 4, successively two welds are made on one side, then two welds are made on the other side, up to the edges of the plate. In other words, the plane bisecting the two planes on which the cross weld is made is perpendicular to the plane bisecting the two planes corresponding to the cross weld along a given plate.

This makes it possible to compensate for deformations due to welding shrinkage, resulting in a highly accurate assembly. The tests carried out were carried out in the special case described here, i.e. when the plates intersect at right angles, the plane PK1''? Intersection of plates 2'' and 4. The best results are obtained by arranging the reso-beam symbolized by the arrow 2 in such a way as to form a 45' corner with the wrappers. Here again spot welding is performed with overlap to provide a continuous weld line. It is very important to create a well-balanced welded product in order to compensate for each other's deformation. This is done not only by placing the laser beam on the bisecting plane of each two planes, but also by placing the two
It is obtained by making a weldment at a face angle. In the example described here, the value of ff1ll for the angle between the direction of the beam and the intersection line of the plates is 45''', where the plates are welded at 6mm wide and have a rectangular width of 12.5mm. We limit the rank, but its value can be easily modified as a function of the lattice plane. However, the best result is 4
Obtained at an angle of 5°. This value should be used if possible. The grid 1 is mounted on a moving support and can be moved to continuously produce the welds of all cross sections 6. When all the Sm objects are completed, the light alloy holding frame is moved.

In the case where the grid is made from zirconium alloy, which is one of the main objects of the present invention, the grid is placed under neutral gas and in an enclosure with holes or windows that allow the passage of the laser beam. It is advantageous to try to prevent any oxidation. Often a pulse array is used. The beam energy is thus transmitted in a discontinuous manner to limit heating of the parts and enable precision welds, while significantly reducing the risk of deformation and oxidation.

Examples of subsequent welding are illustrated in FIGS. 2-5.

In the broom 2 figure, a grid 1 is placed in an enclosure 5 filled with alnon, the upper wall of which is a glass wall or window 11 allowing the passage of a laser beam 17. lattice l
is surrounded by a light alloy frame 18. The whole device is such that the laser beam always passes perpendicularly to the transparent 1111 to reduce refraction errors that may cause the spot to be welded to be off target. The term "transparent" means that the wall 11 allows the wavelength of the beam used to pass through, and the term "transparent" is used in this sense throughout the rest of the specification. In IEK, it is advantageous to use walls that provide a retroreflection treatment to reduce energy loss as the beam passes through.

The cross-sectional view in FIG. 3 shows that the enclosure 5 rests on a support 19 which is inclined at an angle of up to 45 DEG to the horizontal plane and which is displaceable in this direction by the screw 21 (direction X) K. This movement makes it possible to pass the entire length of the cross section 6 at the end of the beam 17 (which is fixed and vertical thereto), while always forming an angle of 45° with the intersection line of the plates. . The device is placed on a table 27 that allows vertical displacement (direction Z) or horizontal displacement (direction Y perpendicular to the plane of the figure) and continuously moves all cross sections under the beam 17. to bring about. In some cases it is advantageous to provide a device for making it possible to replace the lattice It in the enclosure 5 in a direction perpendicular to the direction X.

FIG. 4 explains the welding sequence. Lattice & end loss part A
is located below the beam and is positioned to effect the welding at one of the dihedral angles of this cross section. The grid is then moved so that the beam follows the path symbolized by line 25, while a weldment is formed at one of the corners of each cross section up to cross section B, while optionally leaving a constant cross section. K to jump and reach the final desired device.

The grid is then rotated a quarter of a turn, so that cross section C replaces cross section B and the other weldment system is 26
is made at point Dt along. The grid is then rotated and the same thing happens in the other plane.

FIG. 5 illustrates the last part of the welding sequence corresponding to line 25 when reaching the vicinity of cross section B.

After welding is performed at the crosses 11 and 32, welding is performed at one of the dihedral angles of the cross section 3.

Next, one reaches the cross section B. Other weldments are made in the following sequence after rotating the grid.

Of course, this is an example and other orders are possible as a function of special cases.

Figure 1116 and Figure 7 split the laser beam. □. □Yo, I'm working on it. We describe an improvement to this method that allows us to create a

In FIG. 6, the beam 15 is tilted at 45°t.
It can be seen that the semi-reflecting mirror 20 of the beam 5 is struck, reflecting a portion of the energy of the beam 5 and giving a beam 15a perpendicular to the beam 5, while transmitting a second beam 15b. Beam 15a strikes another semi-reflecting mirror 22t--which has the same effect as mirror 20. Then beam 1
5a is split into a reflected beam 22a and a transmitted beam 22b, which are reflected by two total reflection mirrors 35, 36 at the intersection of the four root plates and plate 2. Similarly, mirror 24
5b into a reflected beam 24a and a transmitted beam 24b, these beams are reflected by total reflection mirrors 37 and 38 on plate 4.
and is reflected at another intersection of the belt plate. The mirror arrangement is beam 22a.

The terminal ends of 22b, 24a, 24b are each located on one side of the grid and are arranged symmetrically such that they are at the first intersection of plates 2 and 4 and the belt plate, as shown in FIG. 6, for example. will be done. Thus, with a single laser beam, four welds can be made at the same time and asymmetrical welds can be performed to maximize deformation. By changing the grid, the final weldment is successfully made.

Figure 7 shows how to make a cross s6 weld from two sides of the lattice after attaching pivots to the edges of the lattice. Beam 40 first passes through refractor 16 and is split into refracted beams 40aK that strike the surface of the grating and transmitted beam 40b. Beam 40b is reflected by small reflective mirror 28 onto the other side of the grating. The whole device is constructed so that the beams 40a and 401) are υ
It is oriented to form a 45° angle. Thus, two halves of the same cross can be welded simultaneously by two crosses or by one of the two beams. This also allows simultaneous welding at two opposing dihedral angles of the same cross section to create a symmetrical weld and reduce deformation.

Naturally, the number and arrangement of the mirrors can be selected to take into account the total plane and energy losses of the equipment, making the maximum possible number of welds at the same time whenever the beam contacts and splits the mirrors. .

The tests carried out made it possible to obtain Zircaloy 4 grids without deformation and in which the welding beads were not contaminated or oxidized, and these tests were carried out using neodymium-filled 1.
It was carried out with a laser at a wavelength of 0.6 μm and a relaxed wrist.

Figures 8 and 9 illustrate the special construction of the tight enclosure when only the ends of each rim are welded. FIG. 8 shows that the enclosure 42 consists of a base 44 connected to an upper box 46 by a tying or hoisting device 48. The box 46 is provided with a glass plate or transparent wall 45, while the box 46 has a raised lath plate 47 and side glass plates 49. In FIG. 9, box 46 is connected to wall 49.
It can be seen that it has a hexagonal shape with a small transparent wall 50 at 45°. Walls 45 and 47 provide welding II of the ends of the cross section, wall 49 provides the welding of plates 2 and 4 to belt plate 9 and 411150 provides the final plate welding to each other.

The laser beam is still perpendicular to the beam through which it passes. The holding frame 52 with the necessary paces 44 can also be seen. This surrounds the grid to be welded on its lower side and on the 111 side.

The opening 54 in the side of the 7V-memory 52 allows the entire beam to pass through the plate 21? and 4 are welded to the belt plate. On the other hand, the opening 55 at the bottom of the frame allows the lower end of the cross section to be welded. Retention is ensured by a pin 56 which stops the belt plate in the intersection area of the belt plate and plates 2 and 4.

In this case it is an assembly consisting of an enclosure 42, a frame 52 and a grating 1 moving in front of the laser beam. In all cases where it is simply necessary to weld each end of the a-race part, it is advantageous to use an enclosure as shown in FIGS. 8 and 9. Due to its small size, it is easier to remove the 7 spaces present in it, and the assembly consists of sb, gratings and slotted enclosures, allowing for easy handling and keeping the welding location immobile. You can install the grid inside the enclosure with . The fact that several enclosures are used allows installation to improve manufacturing efficiency without significantly increasing cost since the cost of the enclosure is low based on the small size.

It will be appreciated that the embodiments described above are not limiting and that various changes may be made to the structural details of the enclosure.

The method according to the invention thus makes it possible to produce zirconium alloy nuclear reactor mixed grids in a precise manner and without any risk of deformation. Furthermore, the fact that the laser beam is split to produce several weld spots or beads at the same time increases the advantages of operation and limits deformation, while allowing for the production of a uniform S*cus. Finally, the possibility of splitting the beam and the mechanical precision of the grating, which facilitates the positioning of the grating, allows the method of the invention to be automated. If it is only necessary to weld each end of the cross section, the method of the present invention is advantageous as shown in FIG.
Further improvements can be made by using enclosures such as those described in and 9. The present application does not limit mixed grids for nuclear reactors, as this method can also be used to manufacture any other device in which thin, small parts have to be welded.

Finally, the invention is not limited to the embodiments described above and many variations can be made, especially with regard to the order in which the various f# kisses are manufactured and the structure of the rim enclosure, without going beyond the scope of the invention.

[Brief explanation of the drawing]

FIG. 111 is a schematic, perspective and partially exploded view illustrating the general principle of the method according to the invention; FIG. Schematic diagram showing the grid to be welded placed in an enclosure, 1
Figure 13 is a schematic cross-sectional view along the line Feng-Rin of Figure @2, No. 4r.
iA is a schematic perspective view illustrating the grid welding sequence shown in FIG. 2, FIG. 5 is an enlarged view of the lower part of the grid in FIG. IE4, t
Figure IL6 is a schematic diagram showing how the laser beam can be split with the help of mirrors for welding several plates to the belt plate at the same time, figure fIN7 is for welding several cross sections at the same time. A schematic diagram showing how the laser beam can be split by mirrors; FIG. 8 is a schematic longitudinal section of a tight enclosure in the case where the crosses are welded only at their ends; FIG. FIG. 8 is a partial cross-sectional view taken along -IK in FIG. 8; Symbols in the figure: 1... Lattice, 2.4 - Plate, 3... Cross part, 5... Enclosure, 6... Ri07 part, 7... End part, 8... #1, 9...Belt plate, ]O...Sat, 11...Glass wall, 12...Gross hole, 1
3... Welding beam P, 15... Beam, 16... Refraction device, 17... Laser beam, 20... Half-reflection mirror, 21... Screw, 22... Half-reflection mirror, 24...Mirror, 25.26...Beam path (
line), 27...Chisol, 31.32...Cross part, 35.36...Total reflection mirror, 37° 38-...Total reflection mirror, 40...Beam, 42...Enclosure, 44
...Base, 45...Glass wall, 46...Box,
48... Hoop hanging device, 49... Glass plate, 50
... Transparent wall, 52... Holding frame, 54... Opening, 55... l[], 56... Pin, A, B, C
, D...indicate cross portions, respectively.

Claims (1)

[Claims] 1) By virtue of the structural elements of the nuclear reactor being placed in a tight enclosure under controlled atmosphere and in particular by the welding spots that intersect with each other and thereby are created at each end. A method of manufacturing a spaced grid made of thin plates that defines a fixed number of fixed cross sections by single-cell laser welding. 2) a laser beam radiation source located outside the enclosure is used, said enclosure has at least one wall transparent to the wavelength of the laser beam used, and the apparatus -
2. A method as claimed in claim 1, in which the house beam is positioned to pass vertically through Ilt. 3) The method according to claim 1, wherein the welding of the cross portion is performed at least on the intersection portion of the plates. 4) The method of claim 111, wherein the ends of the plate are also welded to the belt plate. 5) A method according to claim 1, wherein the welding is repeated at two opposing dihedral angles of each cross section. 6) Two welds are made successively on one side along each plate, followed by two welds on the other side of the plate to the end of the plate. The method described in section. 7) A method as claimed in claim 1, in which the radar beam is located in a plane subtending each of the two sides so that an angle of approximately 45 DEG is formed by the intersecting lines of the plates. 8) A method as claimed in claim 4, in which a hard light alloy frame is arranged around the outer protective belt plate and the cross sections Ka of the plates are entirely welded. 9) The plate is fixed to the belt plate by welding the two tenons provided at both ends of the plate to the two mortises provided in the belt plate, and the welding is done by spot and o-g-wrap. 1. Method according to claim 4, carried out by means of a laser to obtain a continuous welding line: 0) deflecting and splitting the laser beam, which can make several welds at the same time. 2. A method as claimed in claim 1, in which a mirror is used for the purpose. 11) A tight enclosure containing a laser beam radiation source, controlled air, at least one wall transparent to wavelengths, or in which a grating is preserved during welding operations, and therein 12. Apparatus for carrying out the method according to claim 11, comprising a welded grid placed on a welded grid. 12) A device according to claim 11, in which means can be included in the enclosure to make it possible to displace the frame. 13) A device according to claim 11, wherein the frame is fixed with respect to the enclosure. 14) Claims i which also include mirrors capable of splitting and deflecting the laser beam so that several welds can be made simultaneously! The device according to item IIII. 15) Norconium alloy nuclear reactor mixed grid obtainable by the method according to claim 1 with oxidized and uncontaminated weld lines.